Advantages of Faster Memory Controller
As we have already pointed out in our previous articles, Phenom processors feature a built-in North Bridge with a memory controller and L3 cache working at their own frequency and voltage that do not depend on the frequency and voltage of the main processor core. This is what distinguishes Phenom processors from the previous-generation Athlon 64, which memory controller worked at the same speed as the processor core. The use of individual frequency setting for the built-in North Bridge allows clocking the memory independently of the processor core and thus avoiding DDR2 SDRAM frequency variations that may occur in different processor models. Phenom memory controller always sets correct frequencies for standard DDR2 types no matter what the nominal CPU clock speed actually is.
All currently existing Phenom processors, except the top 9850 model, have their memory controller and L3 cache working at 1.8GHz frequency. Phenom X4 9850 Black Edition pushed this frequency 200MHz higher, its integrated North Bridge now works at 2.0GHz.
So, the memory subsystem of this processor should have also sped up a little. We decided to pay special attention to this matter and double-check the memory subsystem performance of a Phenom X4 9850 Black Edition, when its North Bridge worked at 2GHz and at 1.8GHz frequency like in the younger CPU models.
North Bridge frequency: 2.0GHz
North Bridge frequency: 1.8GHz
The results of our practical memory subsystem measurements speak for themselves. The increase in the frequency of the integrated North Bridge did in fact have a positive effect on L3 cache performance as well as on the memory subsystem speed.
Of course, this also tells on the results in real applications, which you can see from our express-tests session chart:
At the same time, you shouldn’t really hope that North Bridge frequency will have a significant effect on the performance. The performance boost does not exceed 3% at best. On average, 200MHz increase in the memory controller and L3 cache frequency generates about 1% improvement in most benchmarks.